The karyotype, which is a map of a person's chromosomes, shows an extra 21st.
Down Syndrome or Trisonomy 21 is caused by an extra 21st chromosome which happens during cell division. During fetilization between a sperm and an egg, the child recieves 23 sets of chromosomes from the father and 23 from the mother for a total of 46 chromosomes. However, people with DS have a total set of 47 chromosomes. This is called a nondisjunction since there was a problem with the chromosomes seperating properly.
normal cell division
nondisjunction
Nondisjunction simply means that there are more or fewer chromosomes than normal. But in this case, there is one more chromosome than normal.
It's true that older women are at a higher risk for having a child with Down Syndrome, (the chance increases as the woman gets older), but most babies with Down Syndrome are born to women under 35 years of age.
- Down Syndrome or Trisonomy 21 is caused by an extra 21st chromosome which happens during cell division. During fetilization between a sperm and an egg, the child recieves 23 sets of chromosomes from the father and 23 from the mother for a total of 46 chromosomes. However, people with DS have a total set of 47 chromosomes. This is called a nondisjunction since there was a problem with the chromosomes seperating properly.
- Nondisjunction simply means that there are more or fewer chromosomes than normal. But in this case, there is one more chromosome than normal.
- It's true that older women are at a higher risk for having a child with Down Syndrome, (the chance increases as the woman gets older), but most babies with Down Syndrome are born to women under 35 years of age.